Can you limit individual user access time to the internet when you have a router?

When I had a broadband modem, users had to log on to the BT Internet service using their own username and password and we had parental controls (part of BT Internet service) which could limit their usage to whatever we deemed fit. Now we have an 'always on' router they don't have to bother logging onto their BT internet service under their own name - they just open IE or Mozilla and off they go.

So how can I limit a user's internet access time with a BB router?

Cheers

 

Slap them around the ear and tell them to get off!

 

Not necessarily going to enforce it, but I would like to know if it's possible